I've just remembered something I was going to ask.
When I was out for my Sunday run all was fine until after about 100 miles when I had to stop at a junction. On take off there was quite a large screech from the back end (the bike's, not mine).
I tried slowing right down to almost falling over pace over and over again and it wouldn't repeat itself. The next time I stopped however, the screech came back when I took off again.
When I stopped for lunch for about half an hour, the screech stopped altogether for the rest of the trip home. So it only seems to happen when it's hot.
I took the bike up to work the next day (just a short 10 mile hop) and despite stopping at multiple junctions in town it wouldn't make the sound again.
It sounds a little like a loose car fanbelt, so I guess the finger of suspicion points to the drive belt (which is 3000 miles / 2 and a half years old)
